MAP sensor misunderstood

Hello!

I use Haltech sprint 500 ECU and his built in MAP sensor.

According all the Road Tuning proccess there is no mentioned on negetive values from the map sensor, but I get negetive values

when idle and in low rpm before boost.

Why according the course there is no negetive values in MAP on the maps, should i didnt need to get this? where I am wrong? what i need to do?

I cant start tune because it totaly differences kpa values from the explenation videos course

Thanks!

You're confusing MAP and MGP.

MAP is manifold absolute pressure, there is no vacuum on this scale.

MGP is mainfold gauge pressure, 0 is atmospheric pressure or 100kpa absolute pressure, you have minus values below 0 when your manifold is pulled into vacuum and positive numbers when your on boost.

In the ECU Manager software if you click the little Triangle "ruler" Icon labelled "change units" or at the very top choose "Tools" -> "options" a options box pops up and you can choose what units pressure is displayed in.

Kpa (otherwise known as Gauge Pressure) = -100kpa to 160kpa default, where -100 is max vacuum, 0 is Atmospheric pressure and positive numbers are boost

Absolute Kpa = 1.3kpa to 261kpa Default, where 0kpa is max vacuum, 100kpa is atmospheric and into boost from there.

Can also choose Psi which is my preferred method.

Yes it's simply the different ways that the MAP signal can be displayed. I'm sorry if this caused some confusion for you. I talk about gauge vs absolute pressure in the EFI Tuning Fundamentals course if you want a refresher.

Thanks a lot!

Thanks a lot!